In general, a DC/DC converter converts an available direct-current voltage source, for example delivered by a battery, into a predetermined direct-current output voltage, necessary for supplying a load, in which the direct-current output voltage can be greater than or less than the voltage source.
For example, the DC/DC buck voltage converter shown in FIG. 1, only with the elements necessary for the purpose of understanding being shown, includes a pair of switches mounted between a first potential VBAT, for example a direct-current power supply source, and a second potential GND, for example a ground, and connected to one another by an output node 20. The pair of switches consists, for example, of an upper switch POWER_MOS_1 mounted between the first potential VBAT and the output node 20, and a lower switch POWER_MOS_2 mounted between the output node 20 and the second potential GND. The converter also includes an inductive element L in series with a capacitive element C coupled to a load LOAD and mounted between the output node 20 and the second potential GND. The upper switch POWER_MOS_1 and the lower switch POWER_MOS_2 are, for example, MOS (Metal Oxide Semiconductor) power transistors, with a p-channel and an n-channel, respectively, with low residual resistance (resistance of the transistors when on), and make it possible to alternately connect the inductive element L to the first potential VBAT and to the second potential GND. The output node 20 is thus traversed by an output current IL and set at an output potential VLX By switching the circulation of the output current IL traversing the inductive element L, the DC/DC converter provides, to the connection node VOUT between the inductive element L, the capacitor C and the load LOAD, an output voltage VOUT greater than or less than the voltage source VBAT. We can thus define two modes of operation for this converter: a first mode of operation corresponding, for example, to a drop in the output voltage with respect to the input voltage (buck-mode), and a second mode of operation corresponding, for example, to an increase in the output voltage with respect to the input voltage (boost-mode).
Depending on the voltage and/or current information available at the output of the converter, a control circuit, known to a person skilled in the art and not shown here, delivers and sends a control signal to the gates of the transistors in order to modulate the conduction times of these transistors. The control circuit adjusts a cyclic ratio (i.e., duty cycle) of a control signal sent to each of the top and bottom switches POWER_MOS_1, POWER_MOS_2 so as to keep the value of the output voltage constant. The control signal can, for example, be of the pulse-width-modulation (PWM) type.
To regulate the output voltage of the DC/DC converter, there are two types of regulations:
voltage regulation, also called “voltage-mode control”, and
current regulation, also called “current-mode control”.
Even if the voltage-mode control may be easy to implement, the current-mode control may provide better performance. In the current-mode control, the knowledge of the current information traversing, for example, the inductive element of the converter is necessary.
The prior art discloses a current-measuring device (or current-sense circuit) generating a mirror current proportional to the current traversing the inductive element of the converter. The current-measuring device of the prior art, while providing better control, requires a large bandwidth for the amplification module forming part of the current-measuring device.
However, to ensure good stability of the converter, the bandwidth of the amplification module typically should be increased and the current information typically should be the best possible.
While the converter has a finite bandwidth when it operates according to the second mode of operation and with the current-mode control, even in this configuration, a stability problem may arise. The stability of the converter, therefore, may not be optimal.
Moreover, the current-measuring device of the prior art has a gain of which the value is typically set by the manufacturer. It is, therefore, often not possible to adjust the gain of the current measuring device in order to provide better current information.
In this context, an embodiment of the disclosure is intended to propose a current-measuring device free of at least one of the limitations mentioned above.